1. Field of the Invention
The present invention relates to a boot which a steering rack boot and a constant velocity joint boot which are used in an automobile are representative of.
2. Related Art
As a boot in which a cylindrical large-diameter portion and a cylindrical small-diameter portion are integrally coupled by a bellows portion, there are, for example, a steering rack boot and a constant velocity joint boot. In these boot, a cylindrical small-diameter portion and a cylindrical large-diameter portion respectively come into contact with the surfaces of the other parts, thereby to define the boot inside and the outside.
In these boot, in order to define the boot inside and the outside surely, the cylindrical small-diameter portion and the cylindrical large-diameter portion must be closely brought into contact with the surfaces of the other parts. Of the other parts, particularly a portion in which the cylindrical small-diameter portion is built (a tie-rod in case of a steering rack boot and a constant velocity joint shaft in case of a constant velocity joint boot) moves generally in the diameter direction and the axial direction. Therefore, in order to prevent the cylindrical small-diameter portion from detaching from the other part, it is necessary to bring the cylindrical small-diameter portion into pressure contact with the surface of the other part. In case that a cylindrical small-diameter portion of a general boot is built in the other part, as shown in FIG. 7, the other part 160 is inserted into a cylindrical small-diameter portion 120, and thereafter the outer portion of the cylindrical small-diameter portion 120 in which the other part has been inserted is fastened by a fastening member 105 such as a hose clip, thereby to bring the cylindrical small-diameter portion 120 into pressure contact with the other part 160. Therefore, the work of building the cylindrical small-diameter portion 120 in the other part 160 requires two steps including an insertion step of inserting the other part 160 into the cylindrical small-diameter portion 120 and a fastening step of fastening the other part 160 and the cylindrical small-diameter portion 120 by the fastening member 105. Therefore, according to the conventional boot, the work of building the cylindrical small-diameter portion 120 in the other part 160 (built-in work) is complicated, so that there is a problem that the cost necessary for the built-in work is high. Further, in order to define surely the inside of the boot 101 from the outside, it is necessary to build the cylindrical small-diameter portion 120 in the predetermined portion of the other part 160. Therefore, in the built-in work, it is necessary to locate the built-in position of the cylindrical small-diameter portion 120 in relation to the other part 160, and locate the built-in position of the fastening member 105 in relation to the cylindrical small-diameter portion 120. This also causes the complicated built-in work and the high cost for the built-in work.
In view of such the circumstances, technology in which a cylindrical small-diameter portion and a fastening member are previously integrated to facilitate the built-in work has been also proposed (refer to, for example, JP-UM-A-2-25776). In a boot disclosed in JP-UM-A-2-25776, as shown in FIG. 8, a fastening member 105 is buried in a cylindrical small-diameter portion 120. Accordingly, when the cylindrical small-diameter portion 120 and the fastening member 105 are built in the other part 160, the cylindrical small-diameter portion 120 comes into pressure contact with the other part 160 by elasticity of the cylindrical small-diameter portion 120 itself and elasticity of the fastening member 105. Therefore, this type boot has an advantage that the
above-mentioned fastening step is not required.
The fastening member in the boot disclosed in FIG. 8 is formed, as shown in FIG. 9, in the shape of a split ring (which is nearly cylindrical and the shape in which a part of a peripheral wall 154 is cut along an axis with a full length in the axial direction). Therefore, when the fastening member 105 expands its diameter, a cut portion 152 cleaves. Accordingly, since contact pressure of the cylindrical small-diameter portion 120 with the other part 160 is greatly different according to the position in the circumferential direction of the fastening member 105, the contact pressure of the cylindrical small-diameter portion 120 with the other part 160 is uneven in the circumferential direction. In result, in the conventional boot disclosed in FIGS. 8 and 9, the cylindrical small-diameter portion 120 cannot be stably built in the other part 160.